I took a 400 out of a 72 Kingwood Estate wagon. Rebuilt it with a .030 bore using dishtop replacement pistons. I found a set of 461 double hump heads with 1.94 valves, put a cam dynamics hydraulic cam with about 280 duration in it along with a torker and 780 Holley. This was a great motor and seemed to be bullet proof. It was a track only rig, but it ran on pump gas. I had a powerglide with a 10" convert and 5.13 gears with 28 inch tall tires on a 63 Nova. It ran 12.30s at 1400 ft elevation and 12.00s at sea level. If I would have changed to a 4.88 gear when I was at sea level it would have gone 11.80s because it really laid down at the top end and was running almost 7000 through the lights. Power peaked about 6750. When I sold the car the motor had over 350 runs on it and was still going strong though I held my breath on every pass as it crossed finish line. It amazes me still that the stock rods and cast crank held up that well.

Personally I think the 400 small block is one of the cheapest ways around to go fast. 406 cubic inches of torque motor will snap your neck back pretty hard.

Pat